JADC - Canadian Dental Association

Temporomandibular Disorders
Early correction of posterior crossbites may help prevent
signs and symptoms of temporomandibular disorder
(TMD). Recent research has shown a correlation between
posterior crossbite and the signs and symptoms of TMD, 30,31
although other studies were unable to find a causal link. 32,33
Therefore, crossbite may be a cofactor in the identification of
patients with TMD, but its role should not be overstated.
Treatment Timing
Maxillary expansion should be directed toward opening
of the midpalatal suture, as this reduces the likelihood of
dental relapse and reduces adverse side effects resulting from
tooth tipping. 34 Sutural expansion is more stable than
dental tipping34 ; therefore, all efforts should be directed
toward maximal sutural opening and minimal dental tipping.
During the deciduous and early mixed dentition stages
(patients under 8 years of age) smaller forces can be used
to achieve sutural expansion, as evidenced by a midline
diastema during expansion or by radiographic images that
show opening of the suture. 18,34 Another advantage of early
treatment (deciduous or very early mixed dentition) is
improvement of maxillary arch length
deficiency secondary to maxillary constriction,
because the permanent
incisors are afforded more space before
or during eruption than if the crossbite
is treated at a later age. When expansion
is carried out during the late deciduous
dentition, the first permanent molars
usually erupt into satisfactory transverse
positions (i.e., without crossbite). 6,17,18
Treatment during the late mixed
dentition is difficult because of exfoliating
deciduous teeth. Older patients in
the early permanent dentition stage (12
years and up) require greater force for
expansion and a faster rate of expansion
because of growth-related changes
in suture biology. 34 a
Treatment of FXB
by maxillary expansion is, therefore,
best carried out during the late deciduous
or early mixed dentition stages.
c
Treatment
Treatment of FXB involves expansion
of the maxillary arch, removal of
occlusal interferences and elimination
of the functional shift. Slow maxillary
expansion can be used during the
deciduous or early mixed dentition
stages. With a W arch (Fig. 1a), quad
helix (Fig. 1b), or a fixed expander,
such as a Haas (Fig. 1c), hyrax (Fig. 1d)
––– Unilateral Posterior Crossbite –––
or superscrew (Fig. 1e), the rate of expansion is a quarter revolution
of the screw every second or third day and the estimated
time to correct the crossbite is 6–12 weeks.
Overexpansion is appropriate, to the point where the lingual
cusps of the upper molars contact the buccal cusps of the
lower molars. The appliance should be left in place to serve as
a retainer for an additional 4–6 months (and for a period at
least equal to that required to correct the crossbite). When a
screw is used as the active mechanism, it can be stabilized
with a ligature wire or with composite to prevent relapse.
If a removable appliance (Fig. 1f) is used, the turning frequency
decreases to every fifth to seventh day, as a faster rate
tends to displace the appliance. This slower approach is also
used for “fan expanders” to prevent the expanding portion of
the appliance from riding occlusally. It is imperative that the
appliance is made with well-fitting clasps to prevent displacement.
Removable appliances are not recommended, as poor
compliance may result in relapse of the previous expansion
and lower success rates. 4,5,19–21
Rapid maxillary expansion can be used in the deciduous,
early mixed or early permanent dentition stages using a Haas,
e f
Figure 1: Appliances that can be used for maxillary expansion: a. W arch;
b. Quad helix; c. Haas; d. Hyrax; e. Superscrew; f. Removable.
JADC • www.cda-adc.ca/jadc • Septembre 2005, Vol. 71, N o 8 • 571
b
d